During an exclusive set visit in London last summer, Renner chatted with E! News' Alicia Quarles about his character's journey within the Marvel Universe. "We get a little bit more, which is great. It's been a lot of fun for [director Joss Whedon] and I to kind of explore the character," the actor said. "I remember there was a sequence we did at the beginning of the movie—it was a big action sequence that's actually at the end of the movie—and there's a little speech I give, and we decided to kind of push that off, because you realize, 'This is kind of the first time we have Hawkeye with a personality speak.' Let's do it when we have a little bit more time.' There's a lot more to explore with this character, as all of them, and the relationships with all the characters. There's a lot more of in this film. It's been a lot of fun."

"We don't go too far into any history or anything of that, but we go into relationships ad there are some cool secrets that are revealed and more relationships that are deepened," Renner, 44, said. "It's great."

The actor didn't say who's who, but it's no surprise that James Spader's Ultron falls into the latter category. "He's so good. He has a difficult job to do," Renner told E! News of Spader's character, an android hell-bent on human destruction. "He does a good job with it."

The Avengers is the third-highest grossing film of all time, but Renner wasn't worried about surpassing that feat with Avengers: Age of Ultron. "We don't feel that pressure. I think that's on a lot of other people," he explained. "We just do our jobs to the best of our ability, and we have a lot of fun doing it."

To see how Hawkeye's relationship with Black Widow develops, watch the video.

Be sure to check out Avengers: Age of Ultron, in theaters May 1. Visit E! Online daily at 8 a.m. PT through May 1 to watch more exclusive on-set interviews.